| In recent years, a large number of coal-fired power plants have been built, while coal is still a very important energy sources in the future. Therefore, the coal-fired emissions of heavy metals pollution in the world have attracted wide attention after emissions of SO2, NOX and CO2 and other pollutants. Take the coal as the main energy structure made china must pay attention to the pollution control.First, the background and research about the nature and hazards, shape measurement and control technology of mercury and arsenic were introduced in detail in the thesis. Next, abundant raw materials, economic, biodegradable, no secondary pollution to the environment, a simple preparation of chitosan and the current of the modified method were presented. Furthermore, the preparation process of chemically modified chitosan sorbents, such as CS/SiO2-SH, CS/SiO2(s)-SH, CS-I-41, CS-S-I-401, CS-S-I-411, and CS-S-I-421, are described. The characterizations of the sorbents were also analyzed using Field Emission scanning electron microscope (FSEM), Fourier transform infra-red spectroscopy (FTIR) and X-ray diffraction (XRD), etc. analysis instruments.Finally, Adsorption experiments of vapor-phase Hg0 and As3+ were carried out using chemically modified chitosan sorbents in a laboratory-scale fixed-bed reactor. The adsorber tests showed that the CS/SiO2 adsorbent after silanization, the mercury removal efficiency of CS/SiO2(s)-SH sorbent reached 80% at 120℃, which was about three to four times more than at 80℃. The sorbents of CS-S-I-421 have the best capacity of mercury removal, which almost had the mercury capture efficiency of 100% for a long time. The mercury removal efficiencies of these sorbents increased with temperature. Moisture presence can increase the chemically modified chitosan's capacity of mercury uptake, due to their unique physicochemical properties. Regarding to the As3+ adsorption results, chitosan exhibited a better adsorption for As3+ than that of iodine-modified chitosan.
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